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[RFC PATCH v2 6/6] driver core: add compatible string in sysfs for platform devices

Nipun Gupta posted 6 patches 3 years, 7 months ago
[RFC PATCH v2 6/6] driver core: add compatible string in sysfs for platform devices
Posted by Nipun Gupta 3 years, 7 months ago 
This change adds compatible string for the platform based
devices.

Signed-off-by: Nipun Gupta <nipun.gupta@amd.com>
---
 Documentation/ABI/testing/sysfs-bus-platform |  8 +++++++
 drivers/base/platform.c                      | 23 ++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-platform b/Documentation/ABI/testing/sysfs-bus-platform
index c4dfe7355c2d..d95ff83d768c 100644
--- a/Documentation/ABI/testing/sysfs-bus-platform
+++ b/Documentation/ABI/testing/sysfs-bus-platform
@@ -54,3 +54,11 @@ Description:
 		Other platform devices use, instead:
 
 			- platform:`driver name`
+
+What:		/sys/bus/platform/devices/.../compatible
+Date:		August 2022
+Contact:	Nipun Gupta <nipun.gupta@amd.com>
+Description:
+		compatible string associated with the device. This is
+		a read only and is visible if the device have "compatible"
+		property associated with it.
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 51bb2289865c..94c33efaa9b8 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -1289,10 +1289,25 @@ static ssize_t driver_override_store(struct device *dev,
 }
 static DEVICE_ATTR_RW(driver_override);
 
+static ssize_t compatible_show(struct device *dev, struct device_attribute *attr,
+			      char *buf)
+{
+	const char *compat;
+	int ret;
+
+	ret = device_property_read_string(dev, "compatible", &compat);
+	if (ret != 0)
+		return 0;
+
+	return sysfs_emit(buf, "%s", compat);
+}
+static DEVICE_ATTR_RO(compatible);
+
 static struct attribute *platform_dev_attrs[] = {
 	&dev_attr_modalias.attr,
 	&dev_attr_numa_node.attr,
 	&dev_attr_driver_override.attr,
+	&dev_attr_compatible.attr,
 	NULL,
 };
 
@@ -1300,11 +1315,19 @@ static umode_t platform_dev_attrs_visible(struct kobject *kobj, struct attribute
 		int n)
 {
 	struct device *dev = container_of(kobj, typeof(*dev), kobj);
+	const char *compat;
+	int ret;
 
 	if (a == &dev_attr_numa_node.attr &&
 			dev_to_node(dev) == NUMA_NO_NODE)
 		return 0;
 
+	if (a == &dev_attr_compatible.attr) {
+		ret = device_property_read_string(dev, "compatible", &compat);
+		if (ret != 0)
+			return 0;
+	}
+
 	return a->mode;
 }
 
-- 
2.25.1
Re: [RFC PATCH v2 6/6] driver core: add compatible string in sysfs for platform devices
Posted by Greg KH 3 years, 7 months ago 
On Wed, Aug 17, 2022 at 08:35:42PM +0530, Nipun Gupta wrote:
> This change adds compatible string for the platform based
> devices.

What exactly is a "compatible string"?

> 
> Signed-off-by: Nipun Gupta <nipun.gupta@amd.com>
> ---
>  Documentation/ABI/testing/sysfs-bus-platform |  8 +++++++
>  drivers/base/platform.c                      | 23 ++++++++++++++++++++
>  2 files changed, 31 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-platform b/Documentation/ABI/testing/sysfs-bus-platform
> index c4dfe7355c2d..d95ff83d768c 100644
> --- a/Documentation/ABI/testing/sysfs-bus-platform
> +++ b/Documentation/ABI/testing/sysfs-bus-platform
> @@ -54,3 +54,11 @@ Description:
>  		Other platform devices use, instead:
>  
>  			- platform:`driver name`
> +
> +What:		/sys/bus/platform/devices/.../compatible
> +Date:		August 2022
> +Contact:	Nipun Gupta <nipun.gupta@amd.com>
> +Description:
> +		compatible string associated with the device. This is
> +		a read only and is visible if the device have "compatible"
> +		property associated with it.

Where is it defined what a compatible property is?

> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index 51bb2289865c..94c33efaa9b8 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -1289,10 +1289,25 @@ static ssize_t driver_override_store(struct device *dev,
>  }
>  static DEVICE_ATTR_RW(driver_override);
>  
> +static ssize_t compatible_show(struct device *dev, struct device_attribute *attr,
> +			      char *buf)
> +{
> +	const char *compat;
> +	int ret;
> +
> +	ret = device_property_read_string(dev, "compatible", &compat);
> +	if (ret != 0)
> +		return 0;

Shouldn't you return an error here?

thanks,

greg k-h
Re: [RFC PATCH v2 6/6] driver core: add compatible string in sysfs for platform devices
Posted by Saravana Kannan 3 years, 7 months ago 
On Wed, Aug 17, 2022 at 8:31 AM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Wed, Aug 17, 2022 at 08:35:42PM +0530, Nipun Gupta wrote:
> > This change adds compatible string for the platform based
> > devices.
>
> What exactly is a "compatible string"?

Didn't read the rest of the patches in the series yet, but Nack to
this. This info is already available under:

<device folder>/of_node/compatible for any device in any (or at least
most) bus that was created from an of_node.

Unless compatible is now also in ACPI. In which case, it's probably be
better to have an of_node like symlink.


-Saravana

>
> >
> > Signed-off-by: Nipun Gupta <nipun.gupta@amd.com>
> > ---
> >  Documentation/ABI/testing/sysfs-bus-platform |  8 +++++++
> >  drivers/base/platform.c                      | 23 ++++++++++++++++++++
> >  2 files changed, 31 insertions(+)
> >
> > diff --git a/Documentation/ABI/testing/sysfs-bus-platform b/Documentation/ABI/testing/sysfs-bus-platform
> > index c4dfe7355c2d..d95ff83d768c 100644
> > --- a/Documentation/ABI/testing/sysfs-bus-platform
> > +++ b/Documentation/ABI/testing/sysfs-bus-platform
> > @@ -54,3 +54,11 @@ Description:
> >               Other platform devices use, instead:
> >
> >                       - platform:`driver name`
> > +
> > +What:                /sys/bus/platform/devices/.../compatible
> > +Date:                August 2022
> > +Contact:     Nipun Gupta <nipun.gupta@amd.com>
> > +Description:
> > +             compatible string associated with the device. This is
> > +             a read only and is visible if the device have "compatible"
> > +             property associated with it.
>
> Where is it defined what a compatible property is?
>
> > diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> > index 51bb2289865c..94c33efaa9b8 100644
> > --- a/drivers/base/platform.c
> > +++ b/drivers/base/platform.c
> > @@ -1289,10 +1289,25 @@ static ssize_t driver_override_store(struct device *dev,
> >  }
> >  static DEVICE_ATTR_RW(driver_override);
> >
> > +static ssize_t compatible_show(struct device *dev, struct device_attribute *attr,
> > +                           char *buf)
> > +{
> > +     const char *compat;
> > +     int ret;
> > +
> > +     ret = device_property_read_string(dev, "compatible", &compat);
> > +     if (ret != 0)
> > +             return 0;
>
> Shouldn't you return an error here?
>
> thanks,
>
> greg k-h
RE: [RFC PATCH v2 6/6] driver core: add compatible string in sysfs for platform devices
Posted by Gupta, Nipun 3 years, 7 months ago 
[AMD Official Use Only - General]



> -----Original Message-----
> From: Saravana Kannan <saravanak@google.com>
> Sent: Wednesday, August 17, 2022 9:34 PM
> To: Greg KH <gregkh@linuxfoundation.org>
> Cc: Gupta, Nipun <Nipun.Gupta@amd.com>; robh+dt@kernel.org;
> krzysztof.kozlowski+dt@linaro.org; rafael@kernel.org; eric.auger@redhat.com;
> alex.williamson@redhat.com; cohuck@redhat.com; Gupta, Puneet (DCG-ENG)
> <puneet.gupta@amd.com>; song.bao.hua@hisilicon.com;
> mchehab+huawei@kernel.org; maz@kernel.org; f.fainelli@gmail.com;
> jeffrey.l.hugo@gmail.com; Michael.Srba@seznam.cz; mani@kernel.org;
> yishaih@nvidia.com; jgg@ziepe.ca; linux-kernel@vger.kernel.org;
> devicetree@vger.kernel.org; kvm@vger.kernel.org; okaya@kernel.org; Anand,
> Harpreet <harpreet.anand@amd.com>; Agarwal, Nikhil
> <nikhil.agarwal@amd.com>; Simek, Michal <michal.simek@amd.com>; git
> (AMD-Xilinx) <git@amd.com>
> Subject: Re: [RFC PATCH v2 6/6] driver core: add compatible string in sysfs for
> platform devices
> 
> [CAUTION: External Email]
> 
> On Wed, Aug 17, 2022 at 8:31 AM Greg KH <gregkh@linuxfoundation.org>
> wrote:
> >
> > On Wed, Aug 17, 2022 at 08:35:42PM +0530, Nipun Gupta wrote:
> > > This change adds compatible string for the platform based
> > > devices.
> >
> > What exactly is a "compatible string"?
> 
> Didn't read the rest of the patches in the series yet, but Nack to
> this. This info is already available under:
> 
> <device folder>/of_node/compatible for any device in any (or at least
> most) bus that was created from an of_node.
> 
> Unless compatible is now also in ACPI. In which case, it's probably be
> better to have an of_node like symlink.

We will not be going with platform devices for CDX bus and would
rather have CDX devices:
https://lore.kernel.org/lkml/DM6PR12MB30827577D50AB1B877458923E8799@DM6PR12MB3082.namprd12.prod.outlook.com/
So, this change is not valid for us. We would not be having this in Rev V3.

- Nipun

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